. The structure and development of mosses and ferns (Archegoniatae). Plant morphology; Mosses; Ferns. XII EQUISETINEM The Sexual Organs 447 The prothallia of Equisetum are usually dioecious and, as is usual in such cases, the males are smaller and the antheridia develop first. The latter generally appear in about a month. In E. telmateia there is not so much difference in the appear- ance and size of the male and female plants, and they are not always distinguishable by the naked eye. The first antheridia in E. pratense (Buchtien (i), p. 21), may appear within four weeks on vigorous prothallia
. The structure and development of mosses and ferns (Archegoniatae). Plant morphology; Mosses; Ferns. XII EQUISETINEM The Sexual Organs 447 The prothallia of Equisetum are usually dioecious and, as is usual in such cases, the males are smaller and the antheridia develop first. The latter generally appear in about a month. In E. telmateia there is not so much difference in the appear- ance and size of the male and female plants, and they are not always distinguishable by the naked eye. The first antheridia in E. pratense (Buchtien (i), p. 21), may appear within four weeks on vigorous prothallia, and are found at the tip, or upon the forward margin of the prothallium. After the first marginal antheridia are formed, there is inau- gurated an active division in the cells immediately adjacent, and a sort of meristem is developed from which new antheridia. Fig. 260.—Development of the antheridium, X190. A, Longitudinal section through the antheridial meristem showing antheridia of different ages; B, longitudinal sec- tion of young antheridiura, X375: C, two sections of a terminal, single antheridium, nearly ripe, X190; D, three transverse sections of young antheridium, X190; o, opercular cell. arise, much as is the case in E. telmateia. While in the latter species, as in others, the antheridia may arise at the ends of the prothallial branches, they also may be formed upon a meris- tem quite like the archegonia, and are usually in groups, so that longitudinal sections show antheridia of very different ages, all evidently derived from the activity of the meristem (Fig. 260, A). The development shows a close resemblance to that of the eusporangiate Ferns, and in connection with the other points in the growth of the gametophyte and sexual organs, suggests. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original
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